High Melting Point Research Articles

Feasibility of Melting NbC Using Electron Beam Powder Bed Fusion

High melting point materials such as ceramics and metal carbides are in general difficult to manufacture due to their physical properties, which imposes the need for new manufacturing methods where electron beam powder bed fusion (EB‐PBF) seems promising. Most materials that have been successfully printed with EB‐PBF are metals and metal alloys with good electrical conductivity, whereas dielectric materials such as ceramics are generally difficult to print. Catastrophic problems such as smoking and spattering can occur during the EB‐PBF processing owing to inappropriate physical properties such as lack of electrical, and thermal conductivity and high melting point, which are challenging to overcome by process optimization. Due to these difficulties, a limited level of understanding has been achieved regarding melting ceramics and refractory alloys. Herein, three different substrates of niobium carbide (NbC) are melted using EB‐PBF. The established process parameter window shows a good correlation between EB‐PBF process parameters, surface, and melt characteristics, which can be used as a baseline for a printing process. Melting NbC is proven feasible using EB‐PBF; the work also points out challenges related to arc trips and spattering, as well as future investigations necessary to create a stable printing process.

Current-carrying tribological behavior of copper alloy matrix and molybdenum alloy coating at high current density

Improving the current-carrying friction and wear resistance of copper alloy current-carrying friction subsets effectively is a hot topic. In this paper, a method of preparing high melting point molybdenum-based coating on copper alloy surfaces by laser cladding technology is presented. A large current (106 A/m2) comparison experiment is carried out with a self-made current-carrying friction device, and the failure mechanism is analyzed. The results show that the molybdenum-based coating significantly improves the adhesion problem between the friction partner and the copper alloy substrate, while the thickness of the stress layer caused by the current-carrying friction is reduced by about 7 times. The molybdenum-based coating significantly reduces the surface arc rate and has a lower friction interface temperature, thus retaining the Al2O3 self-lubricating phase. The research in this paper is expected to provide extended research ideas for the surface protection of current-carrying friction subsets of copper alloys.

Chromium diffusion coatings for improving the oxidation behavior of refractory metals at intermediate temperatures

Due to their very high melting points and high mechanical strength at elevated temperatures, refractory metals are promising structural materials for high temperature applications. However, their application is strongly restricted by their insufficient oxidation resistance. In this fundamental study, four different refractory metals (Mo, Nb, Ta, and W) were chromized by pack cementation to investigate the influence of chromium diffusion coatings on their oxidation resistance at intermediate temperatures. Thermodynamic calculations were used to find the most suitable conditions for the pack cementations. The formation of a homogeneous single-phase bcc Cr layer with a thickness below 10 μm on the sample surface was observed on all four refractory metals. In the case of Nb and Ta, intermetallic Cr2X-Laves phases (X = Nb, Ta) formed underneath the bcc Cr layer while an interdiffusion zone formed on Mo. The concentration profiles of the deposited Cr layers were used to determine the diffusion coefficients graphically via Boltzmann-Matano analysis. The Cr-coated samples were analyzed via thermogravimetric analysis at 700 °C and 900 °C for up to 100 h in dry synthetic air. Optical and electron microscopy, EPMA, EBSD and XRD were used to investigate the chromium diffusion layers and the oxide scales.

Novel Sodium Chloride/Aluminum Oxide Powder-Composite Structure with High Shape-Retention Performance for the Encapsulation of a High-Temperature Phase-Change Material

Inorganic phase-change materials (PCMs) with high melting points have great potential for thermal energy storage systems. Sodium chloride (NaCl) has a high melting point (801 °C) and high latent-heat-storage density (482 kJ/kg). However, it is difficult to encapsulate NaCl using a sintered ceramic shell because of its good wettability against ceramics and high volume-expansion capacity during melting. In this study, a novel NaCl/Al2O3 powder-composite structure was developed as highly stable PCM core material for highly stable encapsulation. The shape-retention performance and the mechanism of NaCl/Al2O3 powder-composite structure during melting were investigated. We have successfully fabricated a NaCl/Al2O3 powder-composite structure, which has a higher NaCl volume ratio of 80 vol% than conventional techniques. The gel-like network structure of Al2O3 particles in molten NaCl was a key structure to keep the shape of the composite ball and to prevent the evaporation of molten NaCl.

Unveiling structural and optical properties of Sn-doped β-Ga2O3: A correlation of experimental and theoretical observations

This work presents the experimental and theoretical insights into the structural and optical properties of tin (Sn)-doped β-Ga2O3. Sn-doped β-Ga2O3 films were fabricated using the low-pressure chemical vapor deposition (LPCVD) method onto the c-plane sapphire substrate. Further, deposited thin films were characterized for their structural and optical properties. XRD pattern depicts the crystalline nature of β-Ga2O3. The energy band gap (Eg) obtained from UV–Vis spectra has been decreased from 4.82 eV to 4.77 eV for as-deposited β-Ga2O3 to Sn-doped β-Ga2O3, respectively. However, an increase in absorbance has been observed in Sn-doped β-Ga2O3 films. Further, the first principle study based on density functional theory (DFT) has been used to comprehend the effect of Sn doping in β-Ga2O3 films. DFT result reveals the expansion of the lattice parameter of intrinsic β-Ga2O3 on the introduction of the Sn atom. Furthermore, a reduction in Eg has been observed upon Sn doping into the β-Ga2O3 structure similar to the experimental results. The reason behind the reduction in the Eg may be due to the Sn-5s energy level at the bottom of the conduction band as revealed in density of state (DOS) investigations. Also, the DOS results of Sn-doped β-Ga2O3 suggest that the atom has tended to form the ionic bond characteristics with the introduction of Sn into the β-Ga2O3, where the free electrons of the Sn-5s orbital state will fill the conduction band and may improve the conductivity. Additionally, optical properties such as reflectance and dielectric loss of function have been investigated. The reflectance and dielectric loss of function result proposed that more energy was absorbed when Sn was introduced to β-Ga2O3. Therefore, our observation suggests that upon Sn doping into β-Ga2O3, optical as well as structural properties were improved and these improved properties may be useful for optoelectronic devices.Novelty statementβ-Ga2O3 is an emerging material for optoelectronic device applications due to its excellent wide energy band gap, high critical electric field strength, high melting point, high Baliga figure of merits (BFOM), and exceptional physical and chemical stability. However, intrinsic β-Ga2O3 suffers from poor mobility and surface defects. Therefore, β-Ga2O3 needs a dopant material to enhance its' structural and optical properties. In this case, Sn doping may improve the optoelectronic properties of β-Ga2O3. Therefore, detailed theoretical and experimental investigations on Sn-doped β-Ga2O3 become necessary to understand inside phenomena. However, lots of experimental and theoretical works have been performed on Sn-doped β-Ga2O3. But, to date, there is no available report related to the correlation of theoretical and experimental data-based studies on Sn-doped β-Ga2O3. In this work, we have explored the structural and optical properties of Sn-doped β-Ga2O3 thin films deposited by the LPCVD method on the c-plane sapphire substrate. Further, the experimental results obtained were correlated with the first principal based DFT results. Our observation suggests that upon Sn doping into β-Ga2O3, optical as well as structural properties were improved and these improved properties may be useful for optoelectronic devices.

Temperature‐responsive palm oil‐based‐oleogels for encapsulation of D‐limonene: effect of fat crystallisation and melting point

SummaryD‐limonene is an important flavouring ingredient with a wide range of applications. However, its high volatility and low stability have severely impacted its application in the food industry. To address these limitations, temperature‐flavour release control system is expected to be established to reduce the loss of D‐limonene during processing and storage, as well as to control its release by temperature. The aim of the current study is to construct an oleogel system to encapsulate D‐limonene using carnauba wax as a gelling agent and palm oils (POs) as the base oil. POs with 24 °C, 38 °C, 42 °C, 48 °C, and 52 °C melting points were selected to systematically investigate the effects of the base oil melting point on the crystal morphology, interactions, physicochemical properties, microstructure, and D‐limonene release of the oleogels. The enthalpy of melting, enthalpy of crystallisation, hardness, stickiness, and gel strength increased in oleogels prepared using POs with a higher melting point. In addition, the oil‐binding capacity (OBC) (>95%) of the oleogels increased with the base oil melting point, while the fat crystal distribution became more homogeneous and denser. Based on the influence that extraction temperature has on the concentration of released D‐limonene (a lower concentration of aroma was released from high‐melting‐point POs oleogels at low temperatures (<1.9 mg mL−1), whereas the control group released >2.5 mg mL−1), suitable POs can be selected to achieve the release or retention of the aroma. These results demonstrate that a temperature‐responsive flavour delivery system can be prepared with different PO melting points. The molecular dynamics of flavour release revealed that storage temperature and fat crystalline state impact the cumulative release rate of D‐limonene.

High-Δn tolane-liquid crystal diluters with low melting point and low rotational viscosity

High birefringence (Δn) and low melting point (Tm), high Δn and low rotational viscosity (γ1) are two pairs of contradictory performance parameters. In this work, two high-Δn LC diluters 3PTPF2V and 3PTPFOV are proposed to achieve a fine balance between them. These target compounds containing a rigid tolane core, a lateral fluorine substituent and a buty-3-enyl or allyloxy terminal group were further synthesized. Some experimental instruments, such as POM, DSC, Abbe refractometer, multi-channel liquid crystal evaluation system, were adopted to investigate their properties of mesomorphic phase behavior, Tm, Δn and γ1 by comparing with classical LC diluters 3HHV and V2PTP2V. Meanwhile, density functional theory (DFT) calculations were employed to correlate the experimental results, and their comprehensive effects on two high-Δn LC mixtures were further evaluated. Research results indicated that both target compounds possess low Tm (∼20 °C), low γ1 (∼6.5 mPa·s), and high Δn (>0.26). Performance in high-Δn LC mixture demonstrated that they could effectively decrease Tm and γ1, meanwhile maintain high Δn and Tc values, meaning their potential application prospects in fast-response LC optical devices.

Hybrid HfC‐SiCN matrix for improved oxidation resistance of carbon fiber–reinforced mini‐composites

AbstractHafnium carbide (HfC) is an ultrahigh‐temperature ceramic with high melting point, chemical stability, hardness, and wear resistance. However, its low fracture toughness and poor thermal shock resistance limit its structural applications in extreme environments. In this study, co‐curing of liquid precursors was carried out prior to complete pyrolysis of individual polymeric precursors. First, HfC preceramic polymer precursor was cured, followed by silicon carbonitride (SiCN) precursor curing on a 2D carbon fiber (CF) cloth using the drop‐coating process. The infiltrated CFs were pyrolyzed at 800°C to achieve CF/HfC‐SiCN ceramic mini‐composites. The cross‐linked precursor‐to‐ceramic yield was observed to be as high as 65% when the procedure was carried out in an inert environment. Although stable up to 1200°C, CF/HfC‐SiCN samples demonstrated susceptibility to oxidation at 1500°C in ambient air. The oxidation of HfC in the presence of SiC leads to the formation of a hafnium‐containing silicate (HfxSiyOz) along with hafnia (HfO2). This compound of silicate and hafnia limits oxygen diffusion better than SiO2 and HfO2 individually. The incorporation of SiCN in HfC ceramic led to improved phase stability compared to a neat HfC system. The results of this study also show that the use of liquid‐phase precursors for HfC and SiCN in the polymer‐infiltrated pyrolysis method is a promising approach to fabricating high‐temperature structural ceramic matrix composites with good oxidation resistance.

A metallurgical approach for separation and recovery of Cu, Cr, and Ni from electroplating sludge

Electroplating sludge is extensively produced in chemical precipitation–based treatment of electroplating wastewater. It poses a huge threat to environmental safety if not properly disposed, ascribed to its high contents of heavy metals. An innovative metallurgical approach was proposed a to recycle Cu, Cr, and Ni from it. Ammonia leaching was firstly performed to selectively leach Cu from Cr, in which the Cu oxide and sulfide were leached into the leachate while the Cr oxide and Ni carbide (NiCx) retained in the residue. (NH4)2SO4 increased the Cu leaching rate via increasing the dissolved oxygen amount in the ammonia leachate and converting CuS to Cu2+. Under the optimal conditions, the leaching efficiency of Cu achieved 96.5 % while that of Cr was only 0.1 %. In the followed aluminothermic reduction, C in the leaching residue could be effectively removed via a thermal oxidation, which in turn decreased the formation of a C-containing compound of high melting point and benefited the Cr and Ni recovery. Cr and Ni from the residue were reduced and recovered in a Cr-Ni alloy, and the reductant of Al first changed to a refractory Al2O3 and then transformed to a low melting point 12CaO·7Al2O3 with the additive of CaO. This transformation increased the molten slag fluidity and promoted the separation of Cr-Ni alloy from slag. Moreover, the excessive Al increased the Cr and Ni yields and concentrated all of them to be together. Partial Al was used as reductant, and the other Al transferred into Cr-Ni alloy to decrease its melting point. Cr and Ni contents in the smelting slag could be decreased to 0.11 wt% and 0.12 wt% respectively, showing an efficient recovery. This work provided a high efficiency method to recover Cu, Cr, and Ni from waste electroplating sludge.

Etherification of biobased resveratrol with ethylene carbonate and its crosslinked polymethacrylates

Biobased polyphenols have been widely studied for their renewable and non-toxic properties, and their thermoplastic/thermosetting materials have also been reported. However, most biobased polyphenols have high melting points and resistance to common solvents, which greatly hinder their applications in organic reactions and material synthesis. Herein, a trihydroxyethyl resveratrol (TER) with a relatively low melting point was prepared by an etherification of biobased resveratrol with ethylene carbonate, and TER trimethacrylate (TTM) was synthesized further from TER and methacryloyl chloride in the presence of triethylamine. TER and TTM were characterized by FTIR, NMR, ESI-MS, and DSC. Free radical curing reaction of TTM was conducted at different initiator dosages, and three crosslinked networks (TER-Ans) were obtained. The conversion rate, crosslinking density, Tg, Tα, mechanical properties, and contact angles were influenced highly by the initiator dosages. At the best initiator dosage of 1 wt% BPO, TER-A2 with the highest crosslinking density (42129.3 mol/m3) and the maximum tensile strength (14.3 MPa) was obtained. Green etherification and hydroxylethylation were established to prepare sustainable crosslinked polymethacrylate materials from biobased resveratrol.

Accurate Surface and Finite-Temperature Bulk Properties of Lithium Metal at Large Scales Using Machine Learning Interaction Potentials.

The properties of lithium metal are key parameters in the design of lithium-ion and lithium-metal batteries. They are difficult to probe experimentally due to the high reactivity and low melting point of lithium as well as the microscopic scales at which lithium exists in batteries where it is found to have enhanced strength, with implications for dendrite suppression strategies. Computationally, there is a lack of empirical potentials that are consistently quantitatively accurate across all properties, and ab initio calculations are too costly. In this work, we train a machine learning interaction potential on density functional theory (DFT) data to state-of-the-art accuracy in reproducing experimental and ab initio results across a wide range of simulations at large length and time scales. We accurately predict thermodynamic properties, phonon spectra, temperature dependence of elastic constants, and various surface properties inaccessible using DFT. We establish that there exists a weak Bell-Evans-Polanyi relation correlating the self-adsorption energy and the minimum surface diffusion barrier for high Miller index facets.

Effect of nano-oxides on corrosion resistance of Al2O3–ZrO2–C material

The Al2O3–ZrO2–C material was prepared using tabular alumina aggregates and fines, zirconia-corundum, zirconia-mullite, flake graphite, B4C powder, Si powder and different nano-oxides (nano-ZrO2, nano-TiO2, and nano-Al2O3) as raw materials, the effects of different nano-oxides on the corrosion resistance and microstructure evolution of Al2O3–ZrO2–C material were investigated. The results showed that the high reactivity nano-ZrO2, nano-TiO2, and nano-Al2O3 particles reacted with CaO to generate high melting point phases of CaZrO3, CaTiO3, CaO·6Al2O3 (CA6) at high temperature, which forms a protective layer at the interface between corroded media and samples, inhibiting CaO penetration into the material. Additionally, nano-oxides can fill the pores and increase the density of material, thereby contributing to improving the penetration resistance and corrosion resistance of material.

Simultaneously Improving the Strength and Plasticity of Additively Manufactured 316L Stainless Steel by Adding Aluminum

Due to the special layer‐by‐layer printing process of additive manufacturing (AM), the heat dissipation in the printed material tends to flow mainly along the building direction, which results in the formation of coarse columnar grains in AM metals. The coarse grains are detrimental to the mechanical properties of AM metals, and are not conducive to the lightweight development of AM metal components. This article proposes a printing strategy for adding aluminum to 316L stainless steel. Based on the aluminum‐reinforced strategy, low melting point MnSiO3 particles are transformed into high melting point Al‐containing particles (such as Al2O3), and the grain size of 316L stainless steel produced by direct energy deposition (DED) is refined, resulting in a significant improvement of tensile strength. What is more, the increase in tensile strength of Al‐reinforced 316L does not sacrifice its plasticity. Attributed to the twinning‐induced plasticity effect and good adhesion between Al2O3 particles and matrix, the plasticity of Al‐reinforced 316L is synchronously improved. To be more specific, compared to DED‐316L without adding Al, the yield strength and tensile strength of samples with adding 0.5%wt Al are individually improved by 14.8% and 16.2%; at same time, the uniform elongation and total elongation are increased by 80.4% and 13%, respectively. The printing strategy proposed in this article is expected to provide reference for the strengthening and toughening of AM metals, thereby contributing to the lightweight development of AM components.

Effects of spans on whipping capabilities of aerated emulsions: Reinforcement of fat crystal-membrane interactions

Poor whipping capabilities of anhydrous milkfat based aerated emulsions pose a fresh challenge to food industrial production, limiting their potential applications in tea drinks, coffee, cakes, and desserts. In this study, the effects of high melting- and low melting-Spans on whipping compatibilities of the aerated emulsions were investigated from view of fat crystal-membrane interactions. With an increase in Spans concentration, there was a corresponding decrease in both fat globule size and interfacial protein. However, in comparison with low melting-Span 20 and Span 80, Span 40 and Span 60 with higher melting points have been found to improve anhydrous milkfat crystal matrix in terms of dense (Df > 1.8) and spot-like crystals (5–10 μm). The interfacial film strength was reduced in this case as both long chain-saturated Spans competitively absorb at the membrane, and elasticity-dominant interfacial membrane was further obtained as their crystallization effects. Occurrence and development of partial coalescence of fat globules (>80% at more than 0.5% addition) were therefore promoted with such fat crystal-membrane interactions during whipping, contributing to a significant improvement in whipping capabilities and heat-stable stabilities of foam structures. A mechanism on the effects of Spans on improving whipping capabilities of aerated emulsions was therefore proposed based on the fat crystal-membrane interactions, which will provide guidance to produce high-quality whipped structures for aerated emulsions.

Effect of double-pass friction stir welding and base materials position on the microstructural and mechanical behaviors of the dissimilar aluminum welded joints of AA6061 and AA2017

Friction stir welding (FSW) is a method of joining solid materials, where the parent metal’s melting temperature is below the point of amalgamation. FSW is a successful method for combining various ferrous and non-ferrous matrix materials. Many researchers’ studies suggested that FSW is suitable for both soft and high melting-point materials by changing the conditional attributes. A defect-free dissimilar weld joint of the alloys AA2017 and AA6061 was fabricated for the current investigation, and the effect of multi-pass friction stir welding (MPFSW) on the development of mechanical and different microstructural behaviors has been investigated. Welding conditions were a constant 1600 rpm weld tool rotational speed, a transverse speed is 32 mm min−1, and a tilt angle of 0°. As a consequence of the pinning effect, the results showed that increasing the number of welding passes in FSW from single to double improved the particle dispersion, which in turn improved the tensile strength, and micro-hardness of the FSWed joint. The primary objectives of this study investigate the strength that was improved because of the rise in the number of passes as well as the effective bonding of the materials’ weld interface, which gives tailor-welded blanks (TWBs) a considerably stronger joint. The findings revealed that the TWB joints’ metallurgical and mechanical properties are extremely varied from single-pass to double-pass, and the position of the base materials can significantly affect the joint properties that are produced.

Crystal growth, luminescence, and scintillation properties of Er-doped La2Hf2O7 single crystal

The growth of Er-doped La2Hf2O7 (LHO:Er) single crystals with a high mp of 2413 °C was achieved by the melt-growth method using a tungsten (W) crucible. Polished LHO:Er specimens were obtained from the as-grown crystals. The full width at half maximum of the X-ray Rocking curve on the (222) diffraction peak was 599 arcsec, and the crystals have relatively low crystallinity. The photoluminescence spectra of the polished LHO:Er specimen showed emission peaks originating from the Er3+ ions in both the visible and IR wavelength ranges. It also exhibited scintillation light under X-ray irradiation.

Influence of zinc (Zn) powder on the microhardness characteristic and microstructure properties of stainless steel SS304 hybrid joint using low power microwave heating

AbstractMicrowave hybrid heating (MHH) process is a unique and novel approach of joint materials. Several lightweight materials (medium and high melting point) such as nickel, copper and aluminum have been successfully joined in the past research. However, small dimensions and low melting point of light weight materials such as zinc (Zn) metal or zinc (Zn) powder were always being a challenging mere for creating bond via any joining techniques. The sheets of stainless steel SS304 (17 mm×7.9 mm×0.2 mm) have been fabricated and joined at lap joint by using novel Microwave hybrid heating technique with mini heat chamber of 2.45 GHz of frequency and 200 W–360 W of microwave power, using pure zinc powder (99.9 %) as an interface material. Epoxy rate and exposure time have been varied from 10 % to 20 % and 2 min to 4 min, respectively. A developed heat chamber has been set in domestic microwave oven properly as proposed. To evaluate the microstructure correlation and microhardness at joint interface, the field emission scanning electron microscopy (FESEM – EDS), x‐ray diffraction (XRD) and Vickers hardness were used. For the experimental studies, it had found an excellent bonding was produced at interface layer between the upper and lower sections with good penetration rate of 360 W of microwave power, 4 min of exposure time and 20 % of epoxy rate as the 183.1 HV 0.05 of excellent microhardness and the intermetallic phase of iron‐zinc (FeZn11), nickel‐zinc (NiZn) and nickel‐zinc (NiZn3) were observed at interface layer.

Tensile Strength and Thermal Properties of Polypropylene/Nano-Bentonite Composites with Maleic Anhydride Coupling Agent

Polypropylene is the most widely used polymer material in the automotive industry due to its properties such as good rigidity, high melting point, chemical resistance, and easy processability. Polypropylene is usually added with a filler, namely bentonite, to make polypropylene which has better mechanical and thermal properties. The coupling agent is added to improve the adhesion of the matrix with the surface so that the composite component has better durability. To improve the ability of the filler material, bentonite is converted into nanoparticles. Bentonite nanoparticles are expected to have better mechanical, thermal, electrical, and optical properties than particles with micro or macro sizes due to their large surface area. Based on the description above, it is necessary to study the effect of using bentonite nanoparticles with a coupling agent in the form of Maleic Anhydride-g-PP (MAPP) on the tensile strength and thermal properties of polypropylene composites. The variables of this study are the composition variation (weight %) of polypropylene, coupling agent (MAPP), and bentonite nanoparticles of 100:0:0, 95:0:5, 90:5:5, 85:5:10, 92:3:5, and 87:3:10. The method used in this study uses a twin-screw extruder tool with a temperature of 190°C and then tested regarding its tensile strength and thermal properties. The results showed that the addition of nano-bentonite tends to cause an increase in the decomposition temperature of the sample but does not increase the tensile strength of the composite, so it only functions as a polymer composite filler. While based on Differential Scanning Calorimetry (DSC) testing, the enthalpy value decreases with increasing concentration of coupling agent.

Ambient Catalytic Spinning of Polyethylene Nanofibers.

A novel single-atom Ni(II) catalyst (Ni-OH) is covalently immobilized onto the nano-channels of mesoporous Santa Barbara Amorphous (SBA)-15 particles and isotropic Anodized Aluminum Oxide (AAO) membrane for confined-space ethylene extrusion polymerization. The presence of surface-tethered Ni complexes (Ni@SBA-15 and Ni@AAO) is confirmed by the inductively coupled plasma-optical emission spectrometry (ICP-OES) and X-ray photoelectron spectroscopy (XPS). In the catalytic spinning process, the produced PE materials exhibit very homogeneous fibrous morphology at nanoscale (diameter: ~50 nm). The synthesized PE nanofibers extrude in a highly oriented manner from the nano-reactors at ambient temperature. Remarkably high Mw (1.62×106 g mol-1 ), melting point (124 °C), and crystallinity (41.8 %) are observed among PE samples thanks to the confined-space polymerization. The chain-walking behavior of surface tethered Ni catalysts is greatly limited by the confinement inside the nano-channels, leading to the formation of very low-branched PE materials (13.6/1000 C). Due to fixed supported catalytic topology and room temperature, the filaments are expected to be free of entanglement. This work signifies an important step towards the realization of a continuous mild catalytic-spinning (CATSPIN) process, where the polymer is directly synthesized into fiber shape at negligible chain branching and elegantly avoiding common limitations like thermal degradation or molecular entanglement.

Ambient Catalytic Spinning of Polyethylene Nanofibers

AbstractA novel single‐atom Ni(II) catalyst (Ni‐OH) is covalently immobilized onto the nano‐channels of mesoporous Santa Barbara Amorphous (SBA)‐15 particles and isotropic Anodized Aluminum Oxide (AAO) membrane for confined‐space ethylene extrusion polymerization. The presence of surface‐tethered Ni complexes (Ni@SBA‐15 and Ni@AAO) is confirmed by the inductively coupled plasma‐optical emission spectrometry (ICP‐OES) and X‐ray photoelectron spectroscopy (XPS). In the catalytic spinning process, the produced PE materials exhibit very homogeneous fibrous morphology at nanoscale (diameter: ~50 nm). The synthesized PE nanofibers extrude in a highly oriented manner from the nano‐reactors at ambient temperature. Remarkably high Mw (1.62×106 g mol−1), melting point (124 °C), and crystallinity (41.8 %) are observed among PE samples thanks to the confined‐space polymerization. The chain‐walking behavior of surface tethered Ni catalysts is greatly limited by the confinement inside the nano‐channels, leading to the formation of very low‐branched PE materials (13.6/1000 C). Due to fixed supported catalytic topology and room temperature, the filaments are expected to be free of entanglement. This work signifies an important step towards the realization of a continuous mild catalytic‐spinning (CATSPIN) process, where the polymer is directly synthesized into fiber shape at negligible chain branching and elegantly avoiding common limitations like thermal degradation or molecular entanglement.